Method of making a honeycomb sandwich



1955 E. ACKERLIND METHOD OF MAKING A HONEYCOMB SANDWICH Filed Sept. 9, 1949 INVEN TOR. {2K AGKEflZ/A/O BY M Q United States Patent METHOD OF MAKING A SANDWICH Erik Ackerlind, Redondo Beach, Calif.,

Northrop Aircraft, Inc., Hawthorne, tion of California Application September 9, 1949, Serial No.

2 Claims. (Cl. 154-110) HONEYCOMB assignor to Califl, a corpora- My invention relates to cellular core sandwiches and more particularly to a method of making a cellular core sandwich well adapted for airplane use.

The method of making a cellular core sandwich shown, described, and claimed herein is of particular value in the fabrication faces, or

The core is usually, but not necessarily, formed from corrugated non-metallic sheets, with their touching side walls bonded, also as by a thermosetting plastic. When the cells in the core are hexagonal, as is customary, the name of honeycomb core is often used.

proper bonding, sheets, and heat rating the solvent in the adhesive.

ly solvable only by the use of accurate dies which, for only a few parts of one ind, are not economically feasible.

It is an object of the present invention to provide a method of applying uniform pressure in the fabrication the internal passageways. applied to the core with the edges of the sandwich sealed,

2,700,632 Patented Jan. 25, 1955 Figure 3 is a diagrammatic cross-section of a cellular core sandwich illustrating one manner of heating the sandwich.

Referring to Figure 1, core sheets 1 of resin impregnated cloth, resin impregnated kraft paper, or the like,

are formed in what is known as a B-tlute corrugating machine.

These sheets 1 are then bonded together, by usually so that two opposite a double wall 5. apertures 6 in each flat side 2 so that exists between all cells of the resultant holes 6 will usually be on the order of eter.

The holes a clean passageway honeycomb. These ,1 to 5 in diamcan be formed in a number of ways, such or punching the core sheets 1 after fluting, and then relying on accurate matching during core sheet bonding to produce open passageways. I preter, however,

to drill apertures 6,

the honeycomb block has been fabricated and cut into core sections.

e evacuation of the interior of the honeycomb core causes atmospheric pressure to force the skin panels 10 tightly and uniformly against the core, so that no dies are necessary. Solvent gases are quickly removed, reducing the precuring time.

heating and suction are discontinued, the seal removed, and the completed sandwich is ready as desired.

As the present type of material, both for core be limited 11 is for use outside of the skin sheets. It is also deemed to be Within the scope of the invention to raise the pressure outside of the sandwich over that of the core by any means desired.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise a preferred form of putting the invention into effect, and the invention is, therefore, claimed in any of its forms or modifications Within the legitimate and valid scope of the appended claims.

What is claimed is:

1. The method of forming a structural sandwich from a core having a plurality of cells normally closed by the application of top and bottom skin sheets to the edges of said cells, which comprises creating air passages between all of the cells of said core intermediate the edges of said cells, applying a skin sheet to each side of said core with adhesive therebetween, temporarily sealing the edges of said skin sheets to form an airtight inner space between said sheets in which said cells communicate through said air passages, exhausting gas from the interior of said cells in said space through said air passages to force said skin sheets firmly against said cell edges, heating said sandwish to cure said adhesive, edge seal.

2. The method of forming a structural sandwich from and removing the temporary 30 a core having a plurality of cells normally closed by the application of top and bottom skin sheets to the edges of said cells, which comprises creating air passages between all of the cells of said core intermediate the edges of said cells, applying a skin sheet to each side of said core with adhesive therebetween, applying a sealing member across the edges of said skin sheets to form an airtight inner space between said sheets in which said cells communicate through said air passages, and with the major area of the outside skin sheets directly exposed to atmospheric pressure, exhausting gas from the interior of said cells in said space through said air passages to cause atmospheric pressure to force said skin sheets firmly against said cell edges, heating said sandwich to cure said adhesive, and removing the edge sealing member.

References Cited in the file of this patent UNITED STATES PATENTS 1,607,780 Palmer Nov. 23, 1926 1,909,444 Worrall May 16, 1933 2,056,563 Budd et al. Oct. 6, 1936 2,380,573 Beasecker July 31, 1945 2,385,352. Davis Sept. 25, 1945 2,389,210 Pitman Nov. 20, 1945 2,429,121 Crowley Oct. 14, 1947 2,434,232 Singleton Jan. 6, 1948 2,456,093 Swedlow Dec. 14, 1948 FOREIGN PATENTS 577,705 Great Britain Dec. 14, 1948 

1. THE METHOD OF FORMING A STRUCTURAL SANDWICH FROM A CORE HAVING A PLURALITY OF CELLS NORMALLY CLOSED BY THE APPLICATION OF TOP AND BOTTOM SKIN SHEETS TO THE EDGES OF SAID CELLS, WHICH COMPRISES CREATING AIR PASSAGES BETWEEN ALL OF THE CELLS OF SAID CORE INTERMEDIATE THE EDGES OF SAID CELLS, APPLYING A SKIN SHEET TO EACH SIDE OF SAID CORE WITH ADHESIVE THEREBETWEEN TEMPORARILY SEALING THE EDGES OF SAID SKIN SHEETS TO FORM AN AIRTIGHT INNER SPACE BETWEEN SAID SHEET IN WHICH SAID CELLS COMMUNICATE THROUGH SAID AIR PASSAGES EXHAUSTING GAS FROM THE INTERIOR OF SAID CELLS IN SAID SPACE THROUGH SAID AIR PASSAGES TO FORCE SAID SKIN SHEETS FIRMLY AGAINST SAID CELL EDGES, HEATING SAID SANDWISH TO CURE SAID ADHESIVE, AND REMOVING THE TEMPORARY EDGE SEAL. 